Only have a different pan than the recipe calls for? Enter the original pan and the pan you actually own — this tool works out the area ratio and scales every ingredient quantity for you.
| Diameter | Area (cm²) |
|---|---|
| 15 cm (6 in) | 177 cm² |
| 18 cm (7 in) | 254 cm² |
| 20 cm (8 in) | 314 cm² |
| 23 cm (9 in) | 415 cm² |
| 25 cm (10 in) | 491 cm² |
| 28 cm (11 in) | 616 cm² |
| 30 cm (12 in) | 707 cm² |
Cake recipes are balanced around a specific batter depth in the pan, so the right way to adapt one for a different pan isn't to guess — it's to compare the surface areas of the two pans and scale every ingredient by that ratio. A round pan's area is π × r² (radius squared times pi), a square pan's area is simply side × side, and a rectangular pan is width × length. If your recipe was written for a 20cm round pan (area ≈ 314 cm²) and you only have a 23cm round pan (area ≈ 415 cm²), the ratio is about 1.32 — meaning you'd need roughly 32% more of every ingredient to keep the same batter depth, and the cake will likely bake slightly faster because it's thinner relative to its surface area.
This calculator computes that exact ratio from the dimensions you enter, then applies it to any single ingredient amount you type in, so you can figure out the rest of the recipe by the same multiplier. It deliberately doesn't try to guess a new baking time, because that depends on too many variables the tool can't see — oven behaviour, pan material and colour, and how much batter depth actually changed. As a general rule of thumb, though: if the new pan gives you a thinner layer of batter (larger area for the same or less batter), start checking for doneness earlier than the original recipe's time; if the layer is thicker (smaller area), expect it to need longer and possibly a slightly lower temperature so the outside doesn't overbake before the centre sets.
One practical exception: this method assumes you want the same batter depth and similar bake in the new pan. If you're deliberately making a thinner sheet cake from a recipe meant for a deep round pan (or vice versa), you may prefer to keep the original ingredient quantities and simply accept a different final depth and bake time, rather than scaling the recipe up or down.
Need an actual bake time, not just a rule of thumb? If you're using the same batter amount in a different-size pan (rather than scaling every ingredient by the ratio above), our Cake Baking Time Calculator by Pan Size takes your original pan, its bake time, and your new pan, and estimates a new bake time from the area ratio and how much the batter's depth changes — the missing half of the scaling math this page deliberately leaves out.